Vehicle speed signal
For vehicles without tachograph: Check the circuit between the vehicle speed sensor on the propeller shaft and the coordinator. Check the vehicle speed sensor on the propeller shaft. For vehicles with tachograph: Check the circuit between the tachograph and coordinator. Check the tachograph supply voltage circuit. Check the circuit between the vehicle speed sensor on the propeller shaft and the tachograph. Check whether the tachograph has generated any fault codes.
What you'll see
No driver-visible symptom recorded.
System reaction
No system-reaction text recorded.
Diagnostic depth
The vehicle speed signal from the vehicle speed sensor or tachograph has been implausibly low. On vehicles without a tachograph, the coordinator receives the vehicle speed signal from the vehicle speed sensor. On vehicles with a tachograph, the coordinator receives the vehicle speed signal from the tachograph.
For vehicles without a tachograph, the fault may be due to: Faulty vehicle speed sensor on the propeller shaft. Short circuit in the vehicle speed sensor circuit. For vehicles with a tachograph, the fault may be due to: Short circuit in the circuit between the tachograph and coordinator. Internal fault in the tachograph.